Spinning machines of this type can include, inter alia, ring-spinning machines, open-end (OE) spinning machines and bell-cup spinning machines. Such spinning machines can have a large number of spinning locations or stations and, as a rule, several hundred spinning stations and even in cases of a thousand spinning stations. Each such spinning station can be provided with a spindle or other means for taking up a spinning bobbin or spool and for driving the spinning means at this station to impart a twist of the sliver which is fed through a drafting frame and between the drafting rollers thereof to the spinning location so that the sliver is twisted to form the yarn.
The sliver-feed-stopping unit which may be provided for each such station, generally in the form of a clamp engageable with the sliver upstream or at least some of the drafting rollers of the drafting frame serve, in the case of a thread break, to prevent further intake of the sliver at the respective station thereby interrupting sliver feed until the defect is corrected. This eliminates unnecessary consumption of the sliver and prevents sliver which is fed undesirably and under conditions in which it cannot be spun into yarn, from detrimentally affecting the moving parts of the spinning station and creating a situation requiring clearing of the sliver fibers.
When there is a yarn break, moreover, continued feed of the sliver through a drafting frame may cause the sliver which continues to be fed uncontrollably to wind up on an upper or lower drafting roller so that the drafting frame can be detrimentally affected.
In OE spinning machines, in addition, the uncontrolled feed of the sliver following a unit break can plug the spinning unit at the spinning station.
As a consequence, a variety of yarn feed interrupters have been provided heretofore and in general such devices have been electrically operated, i.e. tripped by an electric current pulse. The current pulse energizes a solenoid or magnet coil which can release or actuate a mechanical device for preventing further in-feed of the sliver at each location suffering a yarn break.
A simple sliver-feed interrupter can be a normally open clamping device which has an element provided for each station so that the element is released upon detection of a yarn break at each station to clamp off further advance of the sliver.
Each clamping element is associated with an electromagnet which can displace a member retaining the clamping element in its open position when the coil of that device receives a current pulse, the element moving into its closed position.
When the yarn break is cured by the operator or by the automatic yard-tying carriage, the drafting frame is again closed and/or the clamping device reopened so that the sliver or slivers will once more be fed to the respective spinning stations and will be drawn and spun.
Each electrically actuatable sliver-stopping-device requires for its respective actuation, the electrical energy for a brief time. This energy consumption is in the form of a current pulse which has a duration of, for example, 10 to 20 milliseconds.
Thread breakages arises relatively seldomly and are distributed statistically over the spinning frame. In normal operations of a spinning machine, it is not a problem to have available sufficient electrical energy from even a comparatively low power source for operation of the sliver-feed-stopping units which may simultaneously be actuated because of such statistically distributed yarn breakages.
However, under certain operating conditions, problems arise.
These operating conditions include restarting of a machine from standstill, operation of a part of the machine, where only some of the spinning stations are activated, and like conditions which tend to place excessive stress on the yarns and either require a large number of sliver-stopping elements to be actuated simultaneously because of the nature of the operation or because an excessively large number of yarn breakages may occur.
In these conditions and in others, several hundred sensors may detect simultaneous thread breakages and substantially simultaneously energize the respective electromagnets of the sliver-stopping units.
While these occurrences are infrequent, the times at which they recur result in an inordinately high current demand, especially if all of the sliver-feed-stopping solenoids are simultaneously actuated to create a significant problem with respect to continued operation of the spinning machine. It is therefore desirable to abate the high-peak current demand presented by such a phenomenon.